In order to carry out a PCR (Polymerase Chain Reaction) in a “lab-on-a-chip” system, according to our own application PCT/EP2005/055303 with the same application priority, the PCR chamber is filled via a feed channel and emptied via a discharge channel. Temperatures of between 50 and 95° C. are set up during the thermocycling for the PCR. Owing to degassing of dissolved air and thermal expansion of water, the pressure in the chamber thereby increases and displacement of the liquid can take place, leading to uncontrolled conditions during the PCR. In order to avoid this, both the feed and the discharge of the PCR chamber must be closed.
In order to close the PCR chamber, a mobile, resilient membrane or foil may be pressed onto the respective channel, for example the feed channel. To this end, a mechanical force must be exerted. Various valve-drive systems are known from the prior art.
WO 2004/042357 A2 discloses the use of microvalves for microfluidic instruments according to the “lab-on-a-chip” type. This document refers to a prior publication in Micromechanics & Microengineering, New York, N.Y., US, vol. 4, No. 4, December 1994, pages 157 to 171, ISSN XP000863761, in which an overview of a very wide variety of valve designs in microfluidic instruments of the associated actuators are given. As examples, electromagnetically, electrostatically, pneumatically, piezoelectrically or by means of shape changes by memory metals or bimetals in conjunction with counter pressure springs are given. A specific application in connection with a PCR is not revealed therefrom.
For the development of a cost-effective, small-volume device, especially for PCR on a “lab-on-a-chip” arrangement, a suitable principle must be selected from the known systems since increasing the complexity would entail an increase in the costs and the device volume.